Ball bearing detector

[charliecoutas]

I think I may have stunbled on a good solution. I thought about Hall Effect devices, but they only detect magnetic fields. My balls aren't magnetic (Fanie, no don't) and if they were that would cause another problem if two were in the hopper together.

So I ordered this (sorry about the length of it):

https://www.amazon.co.uk/AZDelivery-Linear-Magnetic-Sensor-Arduino/dp/B07DPVTKBB/ref=sr_1_6?crid=2UZJ5NCBVBHEE&dib=eyJ2IjoiMSJ9.1UlCsWl5x9oaWv6UlKU-MpwYz8RBX70Z3bZJX1Dn7WI3dpafXC_TS2dUzuHLnNo5QcIXqrZRsYBiEURyluqDE4OGXolMGcW68QbfEenkRoAxRDX7q5yajhWJ0OwE4E9H5T_6RnUJbSmvSuMkKqXGwdy6lCLqmqcy5D_G6d8-iTtSR4h0FHlZ0BacrMHKNwG6aPii6dIEPi-M86uBTC_kyCKu04us6Su7ZFDCjy_g4cQI7Gci1CvP_4xhUjkO4ws19woYaQ1FjzmFnNviyvp7_xsiPFYyp26U8NHBFagNSik.SY9PgB2mkmqE3m0Hg7W12HG5dLIZa2I5AZ4liYBDWOs&dib_tag=se&keywords=hall%2Beffect%2Bsensor&qid=1753978128&sprefix=hall%2Beffect%2Caps%2C98&sr=8-6&th=1

I thought that by placing a magnet a few inches away from it, so that it juuussstt turned on the Hall sensor. Then if a ferrous object came near then it would detect it. And it does, several inches can easily be had. So guys, I feel a bit of a fraud now after all the ideas you have put forward.

Thoughts?

Charlie

[david]

Sounds like an excellent plan.  So the ball eclipses the magnet's field and the device turns off?
Your new widget should get really excited when the solenoid goes off.
Top marks for originality and simplicity.

Cheers,
David

[charliecoutas]

Thanks David. Yes, the permanent magnet is mounted about 2 inches away from the sensor. There is just enough flux to turn Mr Hall on but when the ball comes within that field, it robs enough flux to turn the sensor off.

I did worry about what happens to the Hall chip when the solenoid goes off but ChatGPT says it is unlikely to cause permanent damage. The sensor will certainly be surprised but it will have quite a long time to recover.

[See_Mos]

Came to this thread a bit late but the first thing that comes to mind is NAMUR inductive proximity sensors which are used to detect the position of machine slides toothed gear wheels etc.  The big problem is the cost. RS have https://uk.rs-online.com/web/p/proximity-sensors/4809075?gb=s at £29.82.

The other easy option would be an I.R. LED light source and detector.

[charliecoutas]

I want it to look like magic, so no holes for IR light sources etc. and the cost of the magnetic sensor is too high.

Les came up with a very clever idea of changing the clock frequency of a PIC by using an air-cored coil instead of a crystal. A loop counted how many times the actual RC clock changed compared to the LC clock, and if enough change, then that indicated that a ball was nearby. I was concerned that this might take to long, or not have a predictable delay, but then I discovered Hall Effect devices

I am going with a Hall effect detector where the steel ball robs the Hall device of the magnetic flux that comes from a magnet nearby. Like all these things, it's not quite as easy as I thought. I'll report back before long.

Charlie

[Fanie]

I would draw a hopper with a cavity inside where you can fit all your obscured parts in and 3D print it.
The stand itself and the hopper pillar could fit the battery(s).  Nothing would be visible from the outside.

For an on/off switch you can even use a reed switch and a small cavity to place the magnet so it starts.  The reed ends are more sensitive for switching than the center.

Your idea of detecting and accelerating should work well for some pendulum model and even for a magnetic suspended object rotating.

There are some very impressive models moving through a cavity that is mesmerizing to watch.  The models you can put up is endless and can be truly fascinating.
 

[charliecoutas]

Fascinating indeed. I thought of a perpetual Newtons Cradle but on looking on the Internet there are lots of them. I like your idea of putting everything in the hopper. The accelerating electromagnet as well?

Charlie

[Fanie]

Here is the Chinese model.



I edited the image so the small motor and the rubber disk is visible.
Your inductors would sit below each other where the motor is.
You can see the battery holder at the back.

Of course all can be concealed if you design your own model.

The hopper is shallow so the balls roll about before falling in the hole, which makes it interesting to look at.

To make it even more interesting (if you go the motor method) is that the rubber disk would catch the ball when off, if you add a motion sensor it could start and run with someone present.  When they leave the model stops.

[Fanie]

Here is another interesting one.

The gears are used to elevate the marbles, the cavity in the gear has the marble run into it, hold it in place while lifting and when reaching the top the marble rolls out.  All done by changing the cavity in the gear's slopes.  In this model, the first gear lift the marbles half way, the marble runs out to the second gear which then lifts it to the top.  If covered the gears would create the impression that the marbles disappear and by magic re-appear when they drop out to run downhill through the maze.